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<td class="header-group page-location"><a href="../refmanual.html" class="navigation-link">Front Page</a> / <a href="./iterators.html" class="navigation-link">Iterators</a> / <a href="./iterator-metafunctions.html" class="navigation-link">Iterator Metafunctions</a> / <a href="./advance.html" class="navigation-link">advance</a></td>
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<div class="section" id="advance">
<h1><a class="toc-backref" href="./iterator-metafunctions.html#id1454">advance</a></h1>
<div class="section" id="id403">
<h3><a class="subsection-title" href="#synopsis" name="synopsis">Synopsis</a></h3>
<pre class="literal-block">
template&lt;
      typename Iterator
    , typename N
    &gt;
struct <a href="./advance.html" class="identifier">advance</a>
{
    typedef <em>unspecified</em> type;
};
</pre>
</div>
<div class="section" id="id404">
<h3><a class="subsection-title" href="#description" name="description">Description</a></h3>
<p>Moves <tt class="literal"><span class="pre">Iterator</span></tt> by the distance <tt class="literal"><span class="pre">N</span></tt>. For <a class="reference internal" href="./bidirectional-iterator.html">bidirectional</a> and
<a class="reference internal" href="./random-access-iterator.html">random access</a> iterators, the distance may be negative.</p>
</div>
<div class="section" id="id405">
<h3><a class="subsection-title" href="#header" name="header">Header</a></h3>
<pre class="literal-block">
#include &lt;<a href="../../../../boost/mpl/advance.hpp" class="header">boost/mpl/advance.hpp</a>&gt;
</pre>
</div>
<div class="section" id="id406">
<h3><a class="subsection-title" href="#parameters" name="parameters">Parameters</a></h3>
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<col width="35%" />
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<tr><th class="head">Parameter</th>
<th class="head">Requirement</th>
<th class="head">Description</th>
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<tbody valign="top">
<tr><td><tt class="literal"><span class="pre">Iterator</span></tt></td>
<td><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a></td>
<td>An iterator to advance.</td>
</tr>
<tr><td><tt class="literal"><span class="pre">N</span></tt></td>
<td><a class="reference internal" href="./integral-constant.html">Integral Constant</a></td>
<td>A distance.</td>
</tr>
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</div>
<div class="section" id="id407">
<h3><a class="subsection-title" href="#model-of" name="model-of">Model Of</a></h3>
<p><a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a></p>
</div>
<div class="section" id="id408">
<h3><a class="subsection-title" href="#expression-semantics" name="expression-semantics">Expression semantics</a></h3>
<p>For a <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a> <tt class="literal"><span class="pre">iter</span></tt> and arbitrary <a class="reference internal" href="./integral-constant.html">Integral Constant</a> <tt class="literal"><span class="pre">n</span></tt>:</p>
<pre class="literal-block">
typedef <a href="./advance.html" class="identifier">advance</a>&lt;iter,n&gt;::type j;
</pre>
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<tr class="field"><th class="field-name">Return type:</th><td class="field-body"><p class="first"><a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Precondition:</th><td class="field-body"><p class="first">If <tt class="literal"><span class="pre">Iterator</span></tt> is a <a class="reference internal" href="./forward-iterator.html">Forward Iterator</a>, <tt class="literal"><span class="pre">n::value</span></tt> must be nonnegative.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Semantics:</th><td class="field-body"><p class="first">Equivalent to:</p>
<pre class="literal-block">
typedef iter i0;
typedef <a href="./next.html" class="identifier">next</a>&lt;i0&gt;::type i1;
<em>...</em>
typedef <a href="./next.html" class="identifier">next</a>&lt;i<em>n-1</em>&gt;::type j;
</pre>
<p>if <tt class="literal"><span class="pre">n::value</span> <span class="pre">&gt;</span> <span class="pre">0</span></tt>, and</p>
<pre class="literal-block">
typedef iter i0;
typedef <a href="./prior.html" class="identifier">prior</a>&lt;i0&gt;::type i1;
<em>...</em>
typedef <a href="./prior.html" class="identifier">prior</a>&lt;i<em>n-1</em>&gt;::type j;
</pre>
<p>otherwise.</p>
</td>
</tr>
<tr class="field"><th class="field-name">Postcondition:</th><td class="field-body"><p class="first last"><tt class="literal"><span class="pre">j</span></tt> is dereferenceable or past-the-end;
<tt class="literal"><span class="pre"><a href="./distance.html" class="identifier">distance</a>&lt;iter,j&gt;::value</span> <span class="pre">==</span> <span class="pre">n::value</span></tt> if <tt class="literal"><span class="pre">n::value</span> <span class="pre">&gt;</span> <span class="pre">0</span></tt>, and
<tt class="literal"><span class="pre"><a href="./distance.html" class="identifier">distance</a>&lt;j,iter&gt;::value</span> <span class="pre">==</span> <span class="pre">n::value</span></tt> otherwise.</p>
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<div class="section" id="id409">
<h3><a class="subsection-title" href="#complexity" name="complexity">Complexity</a></h3>
<p>Amortized constant time if <tt class="literal"><span class="pre">iter</span></tt> is a model of
<a class="reference internal" href="./random-access-iterator.html">Random Access Iterator</a>, otherwise linear time.</p>
</div>
<div class="section" id="id410">
<h3><a class="subsection-title" href="#example" name="example">Example</a></h3>
<pre class="literal-block">
typedef <a href="./range-c.html" class="identifier">range_c</a>&lt;int,0,10&gt; numbers;
typedef <a href="./begin.html" class="identifier">begin</a>&lt;numbers&gt;::type first;
typedef <a href="./end.html" class="identifier">end</a>&lt;numbers&gt;::type last;

typedef <a href="./advance.html" class="identifier">advance</a>&lt;first,<a href="./int.html" class="identifier">int_</a>&lt;10&gt; &gt;::type i1;
typedef <a href="./advance.html" class="identifier">advance</a>&lt;last,<a href="./int.html" class="identifier">int_</a>&lt;-10&gt; &gt;::type i2;

<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( boost::is_same&lt;i1,last&gt; ));
<a href="./assert.html" class="identifier">BOOST_MPL_ASSERT</a>(( boost::is_same&lt;i2,first&gt; ));
</pre>
</div>
<div class="section" id="id411">
<h3><a class="subsection-title" href="#see-also" name="see-also">See also</a></h3>
<p><a class="reference internal" href="./iterators.html">Iterators</a>, <a class="reference internal" href="./tag-dispatched-metafunction.html">Tag Dispatched Metafunction</a>, <a class="reference internal" href="./distance.html">distance</a>, <a class="reference internal" href="./next.html">next</a></p>
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